The endocrine system is a complex system of organs and glands which includes the thyroid and parathyroid. The anatomy of the neck is illustrated in FIG. 1. The thyroid gland regulates many developmental and metabolic processes. Common diseases of the thyroid include goiters, hyperthyroidism, hypothyroidism, benign and malignant nodules, and autoimmune diseases such as Graves' disease. Surgery is the most common treatment for Graves's disease, goiters, benign thyroid nodules, and thyroid cancers.
The parathyroid normally lies within the same region as the thyroid in the neck and functions to control calcium levels in the blood. The most common parathyroid disorder is primary hyperparathyroidism, in which one or more of the parathyroid glands become enlarged and hyperactive. This causes excess secretion of parathyroid hormone and a disruption in normal bone and mineral metabolism. The prevalence of primary hyperparathyroidism has been estimated at 21 cases per 100,000 person-years. In 80% of cases, primary hyperparathyroidism is caused by a single overactive parathyroid gland and surgical removal of the diseased parathyroid gland is the only definitive treatment.
Typically there are four tan parathyroid glands, each approximately 6 to 8 mm in size. They are typically positioned within the neck but can vary in location within the body and are sometimes intrathymic. Due to their small size and variability in position, the parathyroid glands are often difficult to distinguish from surrounding tissue and thyroid in the neck. The parathyroid visually resembles its surrounding tissue and this can extend surgical time during a parathyroidectomy, during which the surgeon is simply searching for the small organ. Accidental removal or damage to healthy parathyroids during parathyroid or thyroid surgery can result in serious complications such as hypocalcemia or hypoparathyroidism. Hypoparathyroidism may result from direct injury, devascularization, and/or disruption of the parathyroid glands. Statistics suggest that temporary and permanent hypoparathyroidism rates are between 4-20% during thyroid surgery. The most common complications of both parathyroid and thyroid surgery are postoperative hypocalcemia, vocal-cord paralysis, and hematoma.
The current surgical procedure for thyroid and parathyroid surgeries involves a systematic search within the neck in which the surgeon is mainly relying on visual inspection to identify target tissues. The incidence of complications occurring due to this subjective method is directly proportional to the extent of thyroidectomy and inversely proportional to the experience of the surgeon. The disadvantages to the current method include the lengthy duration of the surgery, the exploratory nature of the surgery, and the lack of sensitive and applicable preoperative and intra-operative imaging. Confirmation of removal of the diseased parathyroid relies on histopathology or post-operative diagnosis of symptoms. There is a need for reliable methods for identifying the parathyroid glands intraoperatively. Moreover, while surgical guidance systems have been developed and utilized for brain surgery and other organ surgery procedures, none is available for thyroid and parathyroid surgeries.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.